Flexible display device

ABSTRACT

A display device includes a display panel including a folding area and a nonfolding area located around the folding area, a panel bottom member under the display panel and overlapping with the folding area and the nonfolding area, and a first pattern formed in the panel bottom member and overlapping with the folding area.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2017-0183402, filed on Dec. 29, 2017 in the KoreanIntellectual Property Office, the entire disclosure of which isincorporated herein by reference.

BACKGROUND 1. Field

Aspects of embodiments of the present invention relate to a flexibledisplay device.

2. Description of the Related Art

Recently, flexible display devices capable of being bent have beendeveloped. Such flexible display devices can be used in various fieldssince they can be used in a folded or curved form.

Flexible display devices include rollable display devices which can berolled in the form of a roll, foldable display devices which can befolded like paper, and stretchable display devices which can be changedin size.

Flexible display devices are attracting considerable attention asnext-generation display technologies because their volumes can bereduced for easy portability and their screens can be stretched forrealizing a large-area display screen.

Meanwhile, a flexible display device may include a display panel and apanel bottom member disposed under the display panel. The panel bottommember can support the display panel, and can alleviate an externalimpact, thereby reducing an impact transmitted to the display panel. Thepanel bottom member has a thickness, such as a predetermined level ofthickness. As the thickness of the panel bottom member increases, impactresistance may be improved, but flexibility may be deteriorated.

SUMMARY

According to an aspect of embodiments of the present invention, adisplay device has improved flexibility and impact resistance.

According to another aspect of embodiments of the present invention, ina display device, a pattern shape of a lower portion of a display panelmay not be visually recognized on a side of a display screen.

According to one or more exemplary embodiments of the presentdisclosure, a display device includes: a display panel including afolding area and a nonfolding area located around the folding area; apanel bottom member under the display panel and overlapping with thefolding area and the nonfolding area; and a first pattern formed in thepanel bottom member and overlapping with the folding area.

According to one or more exemplary embodiments of the presentdisclosure, a display device includes: a display panel including afolding area and a nonfolding area located around the folding area; anda panel bottom member under the display panel and having a firstthickness in the folding area and a second thickness in the nonfoldingarea, the first thickness being thinner than the second thickness.

However, aspects of the present invention are not restricted to thoseset forth herein. The above and other aspects of the present inventionwill become more apparent to one of ordinary skill in the art to whichthe present invention pertains by referencing the detailed descriptionof some embodiments of the present invention given below.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and features of the present invention willbecome more apparent by describing in further detail some exemplaryembodiments thereof with reference to the attached drawings, in which:

FIG. 1 is a perspective view of a display device according to anembodiment;

FIG. 2 is a cross-sectional view of a display device according to anembodiment, in which the display device is shown folded;

FIG. 3 is a cross-sectional view of a display device according to anembodiment, in which the display device is shown not folded;

FIG. 4 is an enlarged cross-sectional view of a region “A” in FIG. 3;

FIGS. 5 to 9 are cross-sectional views showing panel bottom members ofdisplay devices according to some embodiments;

FIG. 10 is a cross-sectional view of a display device of FIG. 9, inwhich the display device is shown folded;

FIGS. 11 and 12 are cross-sectional views showing panel bottom membersof display devices according to some embodiments;

FIG. 13 is a cross-sectional view of a display device of FIG. 12, inwhich the display device is shown folded;

FIG. 14 is a cross-sectional view showing a panel bottom member of adisplay device according to an embodiment; and

FIGS. 15 and 16 are cross-sectional views showing panel bottom membersof display devices according to some embodiments.

DETAILED DESCRIPTION

Aspects and features of the present disclosure and methods ofaccomplishing the same may be understood more readily by reference tothe following detailed description of some exemplary embodiments and theaccompanying drawings. The present disclosure may, however, be embodiedin many different forms and should not be construed as being limited tothe exemplary embodiments set forth herein. Rather, these exemplaryembodiments are provided so that this disclosure will be thorough andcomplete and will fully convey the concept of the present disclosure tothose skilled in the art, and the present disclosure will be definedwithin the scope of the appended claims.

Cases in which elements or layers are referred to as being located “on”other elements or layers include cases in which one or more other layersor other elements are interposed directly on or between other elements.Meanwhile, cases in which the elements are “directly on” indicate thatno other element or layer is interposed therebetween. Same referencenumerals refer to same or similar constituent elements throughout thespecification. The term “and/or” includes each and every combination ofone or more of the referenced items.

It is to be understood that, although the terms “first,” “second,” etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are used to distinguish oneelement from another element. Thus, a “first” element discussed belowcould be termed a “second” element without departing from the teachingsof the present invention.

In this specification, a first direction X is any one direction in aplane, a second direction Y is a direction intersecting the firstdirection X in the plane, and a third direction Z is a directionperpendicular to the plane.

Like reference numerals designate like or similar elements throughoutthe specification.

Herein, some embodiments of the present invention will be described withreference to the attached drawings.

FIG. 1 is a perspective view of a display device according to anembodiment. FIG. 2 is a cross-sectional view of a display deviceaccording to an embodiment, in which the display device is shown folded.FIG. 3 is a cross-sectional view of a display device according to anembodiment, in which the display device is shown not folded. FIG. 4 isan enlarged cross-sectional view of a region “A” in FIG. 3.

Referring to FIGS. 1 to 4, a display device 1 includes a display panel1000 and a panel bottom member 4000 disposed under the display panel1000. In an embodiment, the display device 1 may further include a touchmember 2000 and a window 3000, which are disposed over the display panel1000.

Unless otherwise defined, as used herein, the terms “upper” or “uppersurface” refer to a side of a display surface with respect to thedisplay panel 1000, and the terms “lower” or “lower surface” refer to aside opposite to the display surface with respect to the display panel1000.

The display device 1 includes a folding area FA and a nonfolding area NFconnected to the folding area FA and disposed around the folding areaFA. The nonfolding area NF is generally located on one plane, and is notfolded, bent, or warped, even when the use form of the display device 1is changed. On the other hand, the folding area FA may be deformed inshape depending on the use form of the display device 1. In other words,the folding area FA may be located on a plane in an unfolded state, butit may be folded, bent, or warped to be disposed along a curved surface.

Although it is shown in the drawings that the display device 1 includesone folding area FA, the present invention is not limited thereto, andthe display device 1 may include a plurality of folding areas FA. Whenthe display device 1 includes a plurality of folding areas FA, thedisplay device 1 may be folded, bent, or warped with respect to each ofthe folding areas FA.

The display panel 1000, which is a panel for displaying an image, maybe, for example, an organic light emitting display panel. In thefollowing embodiments, an organic light emitting display panel isdescribed as the display panel 1000. However, the present invention isnot limited thereto, and other types of display panels, such as a liquidcrystal display panel and an electrophoretic panel, may be applied.

The display panel 1000 includes a plurality of organic light emittingelements arranged on a substrate. The substrate may be a rigid substratemade of glass or the like, or a flexible substrate made of polyimide orthe like. When a polyimide substrate is applied as the substrate, thedisplay panel 1000 may be warped, bent, folded, or rolled.

In an embodiment, the window 3000 is disposed over the display panel1000. The window 3000 is disposed over the display panel 1000 to protectthe display panel 1000 and transmit light emitted from the display panel1000.

The window 3000 may include a transparent material. The window 3000 mayinclude, for example, glass or plastic. The window 3000 may haveflexible properties. In particular, even when the window 3000 includesglass, the window 3000 can maintain flexible properties by using achemical reinforced glass having flexibility.

The window 3000 may be disposed to overlap the display panel 1000 andcover the entire surface of the display panel 1000.

In an embodiment, the touch member 2000 may be disposed between thedisplay panel 1000 and the window 3000. The touch member 2000 may be arigid panel type, a flexible panel type, or a film type. In anembodiment, the touch member 2000 may have substantially the same sizeas the display panel 1000 and may be disposed to overlap the displaypanel 1000, and the side surface of the touch member 2000 may be alignedwith the side surface of the display panel 1000, but the presentinvention is not limited thereto.

The display panel 1000 and the touch member 2000, or the touch member2000 and the window 3000 may be attached to each other by an adhesivelayer 5000, such as an optical clear adhesive (OCA), an optical clearresin (OCR), or a pressure-sensitive adhesive (PSA). For example, thedisplay panel 1000 and the touch member 2000 may be attached to eachother by a first adhesive layer 5001, and the touch member 2000 and thewindow 3000 may be attached to each other by a second adhesive layer5002. The first adhesive layer 5001 and the second adhesive layer 5002may be transparent adhesive layers.

In another embodiment, the touch member 2000 may be omitted. In thiscase, the display panel 1000 and the window 3000 may be directlyattached to each other by the transparent adhesive layer 5000.

In some embodiments, the display panel 1000 may include a touchelectrode unit therein.

The panel bottom member 4000 is disposed under the display panel 1000.In an embodiment, the panel bottom member 4000 may include a supportmember 100 and a buffer member 200, and may be attached to the lowersurface of the display panel 1000 by a third adhesive layer 5003.

In an embodiment, the panel bottom member 4000 may have substantiallythe same size as the display panel 1000 and may be disposed to overlapwith the display panel 1000, and the side surface of the panel bottommember 4000 may be aligned with the side surface of the display panel1000, but the present invention is not limited thereto. In anembodiment, the support member 100 and the buffer member 200,constituting the panel bottom member 4000, may further perform a heatradiation function, an electromagnetic wave blocking function, a patternvisibility preventing function, and/or a strength enhancing function inaddition to a supporting function and a buffering function.

The support member 100 and the buffer member 200 may be provided in anyof various forms, such as a layer, a film, a sheet, a plate, and apanel.

In an embodiment, the support member 100 has substantially the same sizeas the display panel 1000, and may be disposed on the entire lowersurface of the display panel 1000 as described above. The support member100 may be made of a material having rigidity higher than apredetermined level. For example, the support member 100 may be formedof a metal material, such as Invar, which is an alloy of Ni and Cu,stainless steel (SUS), titanium (Ti), or copper (Cu). However, thepresent invention is not limited to the above examples, and may includeany material having sufficient rigidity for supporting the display panel1000. The rigidity may be, for example, 70 GPa.

In an embodiment, the support member 100 can prevent or substantiallyprevent the transmission of light to prevent or substantially prevent apattern H1 of the lower surface of the support member 100 and/or apattern of the buffer member 200 from being visually recognized on theside of the display screen. The support member 100 may include a lightabsorbing material such as black pigment or dye. However, in anembodiment, the support member 100 may include a metal materialabsorbing or reflecting light, and the support member 100 may notinclude a light absorbing material because the support member 100 itselfblocks the transmission of light.

The support member 100 may include the first pattern H1. The firstpattern H1 may be disposed on the lower surface of the support member100 in the folding area FA. In an embodiment, the first pattern H1 has agroove shape recessed inward with respect to the lower surface of thesupport member 100. It is possible to prevent or substantially preventthe first pattern H1 from being visually recognized on the side of adisplay screen by forming the first pattern H1 on the lower surface ofthe support member 100.

In an embodiment, the first pattern H1 may be disposed over the entirefolding area FA. That is, both ends of the first pattern H1 may bealigned at the boundaries of the folding area FA and the nonfolding areaNF. However, the present invention is not limited thereto, and both endsof the first pattern H1 may be disposed in the nonfolding area NF asshown in FIG. 6, or may be disposed in the folding area FA.

In an embodiment, the first pattern H1 may have a line shape extendingcontinuously along the arrangement direction of the folding area FA. Forexample, a cross-section of the first pattern H1 may have an arcuateshape, that is, a tunnel shape extending along the folding area FA.However, the present invention is not limited thereto, and the firstpattern H1 may also include a plurality of patterns separately arrangedalong the arrangement direction of the folding area FA. The plurality ofneighboring patterns may be spaced apart from each other by a distance(e.g., a predetermined distance), and the lower surface of the supportmember 100 and the upper surface of the buffer member 200 may be incontact with each other where no pattern is formed.

In an embodiment, an empty space formed by the first pattern H1 may befilled with air, and an air gap may be defined in a space surrounded bythe support member 100 and the buffer member 200. The air gap not onlyabsorbs an external impact applied to the display device 1, but alsoprevents or substantially prevents the external impact from propagating,thereby improving the impact resistance of the display device 1. Inanother embodiment, the empty space formed by the first pattern H1 maybe filled with an elastic member capable of being flexible and absorbingan external impact.

The first pattern H1 can alleviate the stress due to the folding of thedisplay device 1 as well as perform the above buffering function toimprove the flexibility of the display device 1. Specifically, when thedisplay device 1 is folded, the upper surface of the support member 100is subjected to tensile stress, whereas the lower surface of the supportmember 100 is subjected to compressive stress. When the first pattern H1is formed on the lower surface of the support member 100 subjected tocompressive stress, the spacing of the first patterns H1 is reduced,thereby alleviating the stress.

Moreover, the stress applied to the support member 100 can be alleviatedby changing the thickness of the support member 100. That is, athickness d2 of the support member 100 in the folding area FA may bethinner than a thickness d1 of the support member 100 in the nonfoldingarea NF. The support member 100 may include the first pattern H1 in thefolding area FA, and the thickness d2 of the support member 100 in anarea where the first pattern H1 is formed may be thinner than thethickness d1 of the support member 100 in an area where the firstpattern H1 is not formed.

In an embodiment, since the support member 100 includes a materialhaving rigidity, the flexibility of the support member 100 may decreasecompared to when the support member includes a flexible material.Generally, the rigidity and flexibility of the support member 100 havean inverse proportion relation, and the flexibility thereof decreaseswhen the rigidity thereof increases. The rigidity and flexibility of thesupport member 100 depend on the thickness of the support member 100. Asthe thickness of the support member 100 increases, the rigidity thereofincreases to improve the impact resistance of the display device 1, butthe flexibility thereof decreases to cause folding to become difficult.For example, when the support member 100 is formed to have a samethickness over the entire display device 1, the display device 1 canhave excellent impact resistance or excellent flexibility, but it isdifficult to have both excellent impact resistance and excellentflexibility. On the other hand, when a thickness of the support member100 in the folding area FA is made thinner than a thickness of thesupport member 100 in the nonfolding area NF, the flexibility of thedisplay device 1 can be improved while the impact resistance of thedisplay device 1 is maintained.

In an embodiment, the thickness d1 of the support member 100 in thenonfolding area NF may be about 50 μm to about 100 μm. When thethickness d1 of the support member 100 is about 50 μm or more, thesupport member 100 may have sufficient rigidity and impact resistancefor supporting and protecting the display panel 1000. As the thicknessof the support member 100 increases, rigidity and impact resistance areimproved. However, when the thickness of the support member 100 is toothick, it may be inversely proportional to the thinning of the displaydevice 1 and may be disadvantageous in terms of costs, so that, in anembodiment, the thickness of the support member 100 may be about 100 μm.

When the thickness d2 of the support member 100 in the folding area FAis too thick, flexibility deteriorates. When the thickness d2 thereof istoo thin, it is difficult to support the display panel 1000. In anembodiment, the thickness d2 of the support member 100 may be about 20μm to 30 μm. The thickness d2 of the support member 100 in the foldingarea FA, which may be a minimum thickness of the support member 100,refers to a thickness of the support member 100 at a base point of thefirst pattern H1.

The buffer member 200 is disposed beneath the support member 100. Asdescribed above, in an embodiment, the buffer member 200 hassubstantially the same size as the display panel 1000, and may cover theentire lower surface of the display panel 1000.

The first pattern H1 may be concurrently (e.g., simultaneously) formedtogether with the support member 100, or may be formed by removing apart of the support member 100 after the formation of the support member100. In an embodiment, for example, in a case of forming the supportmember 100 through a rolling process, the first pattern H1 and thesupport member 100 may be concurrently (e.g., simultaneously) formed byforming a predetermined protrusion on a roll. As another example, afterthe support member 100 is formed, the first pattern H1 may be formedthrough a metal etching method or the like. However, the method offorming the first pattern H1 is not limited to the above examples, andmay differ depending on a material constituting the support member 100.

In an embodiment, the buffer member 200 may be integrally formed on thelower surface of the support member 100 without a separate adhesivemember. The buffer member 200 can prevent or substantially prevent thedisplay device 1 absorbing an external impact from being damaged. Thebuffer member 200 may be composed of a single layer or a plurality oflaminated films. The buffer member 200 may include an elastic material,such as polyurethane resin or polyethylene resin. The buffer member 200may be made of a material having higher flexibility than the supportmember 100.

Herein, some other embodiments will be described. In the followingembodiments, description of the same configurations as those of thepreviously described embodiment may be omitted or simplified, anddifferences will be mainly described.

FIGS. 5 to 9 are cross-sectional views showing panel bottom members ofdisplay devices according to some embodiments. FIG. 10 is across-sectional view of a display device of FIG. 9, in which the displaydevice is shown folded.

Referring to FIG. 5, a display device 2 according to an embodiment isdifferent from the display device 1 of FIG. 4 in that a panel bottommember 4002 of the display device 2 further includes a fourth adhesivelayer 5004 disposed between a support member 102 and a buffer member202.

The buffer member 202 may be formed separately from the support member102, and then may be attached to the support member 102 through thefourth adhesive layer 5004. The fourth adhesive layer 5004 may bedisposed in the nonfolding area NA except for the folding area FA wherea first pattern H2 is formed.

In an embodiment, the fourth adhesive layer 5004 may be made of a samematerial as the first to third adhesive layers 5001 to 5003.

Referring to FIG. 6, a display device 3 according to an embodiment isdifferent from the display device 1 of FIG. 4 in that a panel bottommember 4003 of the display device 3 has a first pattern H3 of a supportmember 103 disposed over the folding area FA and the nonfolding area NFas compared with the first pattern H1 of FIG. 4 disposed only in thefolding area FA.

In an embodiment, the first pattern H3 may be mostly disposed in thefolding area FA, and both sides of the first pattern H3 may be disposedin the nonfolding area NF. A base point of the first pattern H3 may bedisposed in the folding area FA, and an area of the first pattern H3disposed in the folding area FA may be greater than that of the firstpattern H3 disposed in the nonfolding area NF.

Referring to FIGS. 7 and 8, panel bottom members 4004 and 4005 ofdisplay devices 4 and 5 may include first patterns H4 and H5 of supportmembers 104 and 105 having a trapezoidal (or rectangular) and triangularcross-section, respectively.

For example, the first pattern H4 may include a trapezoidalcross-section having a flat base surface. In an embodiment, the firstpattern H4 may have an isosceles trapezoidal shape symmetrical withrespect to a center of the folding area FA. When the shape of the firstpattern H4 is symmetrical with respect to the center of the folding areaFA, stress applied to the support member 100 may be uniformly dispersed,such that the flexibility of the display device 4 can be improved.

Similarly to the first pattern H4 of FIG. 7, the first pattern H5 ofFIG. 8 may have a triangular shape that is also symmetrical with respectto the center of the folding area FA.

Referring to FIGS. 9 and 10, a panel bottom member 4006 of a displaydevice 6 according to an embodiment may include a first pattern H6having an uneven shape.

The first pattern H6 may be a surface unevenness formed on a lowersurface of a support member 106. In an embodiment, the first pattern H6may have a shape in which a plurality of grooves recessed with respectto the lower surface of the support member 106 is arranged. In anembodiment, the first pattern H6 includes a plurality of relativelyrecessed concave portions and a plurality of relatively protruded convexportions.

In consideration of the rigidity of the support member 106, the firstpattern H6 may have a shape in which a width of the concave portion isgreater than a width of the convex portion. That is, an amount of theremoved area of the support member 106 may be increased, and a stressapplied to the support member 106 at the time of folding can bealleviated. However, the present invention is not limited thereto, andthe width of the convex portion may be greater than the width of theconcave portion.

In an embodiment, the convex portion of the first pattern H6 is disposedon substantially the same plane as the lower surface of the supportmember 106, or is located inward with respect to the lower surface ofthe support member 106. That is, the convex portion of the first patternH6 may not protrude from the lower surface of the support member 106.Although it is shown in the drawing that the convex portion of the firstpattern H6 is in contact with a buffer member 206, the present inventionis not limited thereto, and the convex portion of the first pattern H6may not be in contact with the buffer member 206.

The interval between the convex portions of the first pattern H6, thatis, the width of the concave portion, may increase with the folding ofthe display device 6, as shown in FIG. 10. As described above, when thedisplay device 6 is folded, the lower surface of the support member 106may be subjected to compressive stress. The first pattern H6 is disposedin the folding area FA subjected to the compressive stress, and theinterval between the convex portions of the first pattern H6 isnarrowed, thereby alleviating the stress. Moreover, the support member106 can more stably support the display panel 1000 by the convexportions of the first pattern H6, and thus the impact resistance of thedisplay device 6 can be improved.

FIGS. 11 and 12 are cross-sectional views showing panel bottom membersof display devices according to some embodiments. FIG. 13 is across-sectional view of a display device of FIG. 12, in which thedisplay device is shown folded. FIG. 14 is a cross-sectional view ofshowing a panel bottom member of a display device according to anembodiment.

Display devices 7, 8, and 9 of FIGS. 11 to 14 are different from thedisplay devices 1 to 6 of FIGS. 1 to 10 in that panel bottom members4007, 4008, and 4009 include second patterns H7, H8, and H9 disposed inbuffer members 207, 208, and 209, respectively.

Referring to FIG. 11, the panel bottom member 4007 includes the secondpattern H7 disposed on an upper surface of the buffer member 207 in thefolding area FA.

Unlike the first patterns H1 to H6, the second pattern H7 may bedisposed on the upper surface of the buffer member 207. Since a supportmember 107 is disposed between the buffer member 207 and the displaypanel 1000, the second pattern H7 of the buffer member 207 is notvisually recognized on the display panel 1000.

Similarly to the first patterns H1 to H6, in an embodiment, the secondpattern H7 may be disposed over the entire folding area FA. In anembodiment, the second pattern H7 may have a line shape extendingcontinuously along the arrangement direction of the folding area FA, ormay have a shape in which a plurality of patterns separated from eachother is arranged.

The second pattern H7 may have any of various cross-sectional shapes,such as an arcuate shape, a rectangular shape, and a triangular shape.

In an embodiment, an empty space formed by the second pattern H7 may befilled with air to form an air gap. The air gap can absorb an externalimpact applied to the display device 7, and can prevent or substantiallyprevent the external impact from propagating, thereby improving theimpact resistance of the display device 7. In another embodiment, theempty space formed by the second pattern H7 may be filled with amaterial having higher flexibility than the buffer member 207.

The second pattern H7 can alleviate the stress due to the folding of thedisplay device 7 in addition to a buffering function. Specifically, whenthe display device 7 is folded, the upper surface of the buffer member207 may be subjected to tensile stress. The surface area of the buffermember 207 in the case in which the second pattern H7 is formed in thefolding area FA is larger than that of the buffer member 207 in the casein which the second pattern H7 is not formed in the folding area FA. Inthis case, the tensile stress is dispersed along the surface of thesecond pattern H7, thereby alleviating the stress applied to the buffermember 207.

Moreover, the stress applied to the buffer member 207 can be alleviatedby changing the thickness of the buffer member 207. That is, a thicknessd4 of the buffer member 207 in the folding area FA may be thinner than athickness d3 of the buffer member 207 in the nonfolding area NF.

Generally, flexibility increases as the thickness of a member decreases,so that the flexibility of the display device 7 can be improved bydecreasing the thickness d4 of the buffer member 207 in the folding areaFA. In addition, a buffering function can be maintained by making thethickness d3 of the buffer member 207 relatively large in the nonfoldingarea NF. In an embodiment, the thickness d3 of the buffer member 207 inthe nonfolding area NF may be about 250 μm to about 300 μm, and thethickness d4 of the buffer member 207 in the folding area FA includingthe second pattern H7 may be about 50 μm to about 100 μm. Here, thethickness d4 of the buffer member 207 in the folding area FA, which maybe a minimum thickness of the buffer member 207, refers to a thicknessof the buffer member 207 at a base point of the second pattern H7.

Referring to FIGS. 12 and 13, the buffer member 208 of the panel bottommember 4008 may include the second pattern H8 having an uneven shape.

In an embodiment, the second pattern H8 may have a shape in which aplurality of grooves recessed with respect to an upper surface of thebuffer member 208 is arranged. In an embodiment, the second pattern H8includes a plurality of relatively recessed concave portions and aplurality of relatively protruded convex portions.

Although it is shown in the drawing that the second pattern H8 has anuneven shape with respect to the upper surface of the buffer member 208,the present invention is not limited thereto, and the second pattern H8having an uneven shape may be formed on a lower surface of the buffermember 208.

As shown in FIG. 13, the second pattern H8 can alleviate a tensilestress applied to the upper surface of the buffer member 208 byincreasing intervals at the time of folding the display device 8.

Unlike the first pattern H6 of FIG. 9, in the second pattern H8, thewidth of the convex portion may be larger than the width of the concaveportion. That is, an area in which the buffer member 208 is removed maybe reduced, thereby maintaining a buffering function. However, thepresent invention is not limited thereto, and the width of the concaveportion may be larger than the width of the convex portion.

Referring to FIG. 14, the buffer member 209 of the panel bottom member4009 may include the second pattern H9 disposed at the lower portionthereof.

The second pattern H9 disposed at the lower portion of the buffer member209 may perform substantially the same function as the first pattern H1of FIG. 3.

FIGS. 15 and 16 are cross-sectional views showing panel bottom membersof display devices according to some embodiments.

Referring to FIGS. 15 and 16, panel bottom members 4010 and 4011 ofdisplay devices 10 and 11 may include both first patterns H10_1 andH11_1 and second patterns H10_2 and H11_2, respectively.

Each of the first patterns H10_1 and H11_1 may be formed on the lowersurface of each of support members 110 and 111, whereas each of thesecond patterns H10_2 and H11_2 may be formed on the upper surface orthe lower surface of each of buffer members 210 and 211.

The first patterns H10_1 and H11_1 and the second patterns H10_2 andH11_2 may be disposed to overlap each other. For example, in across-section, base points of the first patterns H10_1 and H11_1 may besubstantially aligned with base points of the second patterns H10_2 andH11_2.

As described above, the thickness d2 of each of the support members 110and 111 in the folding area FA may be thinner than the thickness d1 ofeach of the support members 110 and 111 in the nonfolding area NF.Further, the thickness d4 of each of the buffer members 210 and 211 inthe folding area FA may be thinner than the thickness d3 of each of thebuffer members 210 and 211 in the nonfolding area NF. In an embodiment,the thickness d2 of each of the support members 110 and 111 in thefolding area FA may be thinner than the thickness d4 of each of thebuffer members 210 and 211 in the folding area FA.

Although it is shown in the drawings that the cross-sectional shapes ofthe first patterns H10_1 and H11_1 are similar to the cross-sectionalshapes of the second patterns H10_2 and H11_2, the present invention isnot limited thereto. For example, each of the first patterns H10_1 andH11_1 may have an arcuate cross-sectional shape, and each of the secondpatterns H10_2 and H11_2 may have a trapezoidal (or rectangular)cross-sectional shape.

When the panel bottom members 4010 and 4011 include both the firstpatterns H10_1 and H11_1 and the second patterns H10_2 and H11_2,respectively, the stress applied at the time of folding the displaydevices 10 and 11 can be more effectively alleviated.

As described above, according to the display device of embodiments, itis possible to improve folding reliability while maintaining impactresistance against an external impact. In addition, it is possible toprevent or substantially prevent a pattern formed on the panel bottommember from being visually recognized on the side of the display screen,thereby preventing or substantially preventing deterioration of anaesthetic sense.

Aspects and effects of the present invention are not limited by theforegoing, and other various aspects and effects are anticipated herein.

Although some exemplary embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions, and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

What is claimed is:
 1. A display device comprising: a display panelincluding a folding area and a nonfolding area located around thefolding area; a panel bottom member under the display panel andoverlapping with the folding area and the nonfolding area; and a firstpattern formed in the panel bottom member and overlapping with thefolding area, wherein the panel bottom member comprises a buffer memberand a support member between the display panel and the buffer member,and the first pattern is recessed from a lower surface of the supportmember.
 2. The display device of claim 1, wherein the first pattern hasa groove shape recessed from the lower surface of the support member. 3.The display device of claim 2, wherein the first pattern has a lineshape extending continuously along the folding area.
 4. The displaydevice of claim 1, wherein the first pattern has an uneven shape on thelower surface of the support member.
 5. The display device of claim 4,wherein the first pattern includes a relatively protruded convexportion, and the convex portion is not protruded from the lower surfaceof the support member.
 6. The display device of claim 1, wherein thesupport member includes a metal.
 7. The display device of claim 6,wherein an end of the first pattern is aligned with a boundary betweenthe folding area and the nonfolding area.
 8. The display device of claim6, wherein an end of the first pattern is in the nonfolding area.
 9. Thedisplay device of claim 1, further comprising a second pattern formed inthe buffer member and overlapping with the first pattern.
 10. Thedisplay device of claim 1, wherein an upper surface of the buffer memberfaces the lower surface of the support member, and wherein the uppersurface of the buffer member overlaps the first pattern.
 11. A displaydevice comprising: a display panel including a folding area and anonfolding area located around the folding area; and a panel bottommember under the display panel and comprising a rigid materialoverlapping with the folding area, the panel bottom member having afirst thickness in the folding area and a second thickness in thenonfolding area, the first thickness being thinner than the secondthickness.
 12. The display device of claim 11, wherein the panel bottommember includes a buffer member, and a first pattern is formed on anupper surface or a lower surface of the buffer member.
 13. The displaydevice of claim 12, wherein the first pattern has a groove shaperecessed from the upper surface or the lower surface of the buffermember.
 14. The display device of claim 12, wherein the first patternhas an uneven shape on the upper surface or the lower surface of thebuffer member.
 15. The display device of claim 11, wherein an intervalbetween an upper surface of the panel bottom member and the displaypanel is constant.
 16. The display device of claim 15, wherein the rigidmaterial includes a metal.
 17. The display device of claim 15, furthercomprising a buffer member at a lower portion of the panel bottommember.
 18. The display device of claim 17, wherein the buffer memberhas a third thickness in the folding area and a fourth thickness in thenonfolding area, and the third thickness is thinner than the fourththickness.
 19. The display device of claim 18, wherein the firstthickness is thinner than the third thickness.